Shoehorning minorities into a film which doesn't call for any wouldn't improve things one bit, and the fact is two roles were shoehorned into the movies to expressly replace white characters (Fury, Heimdall) with black actors. Let's make them female just to get that diversity train going, eh?

How would adding blacks, women and other minorities be shoehorning them into the Avengers? The Avengers have ALWAYS had a diverse "affirmative action" lineup, even from the days when it was considered groundbreaking and risky to do so. Adding Black Panther or War Machine or Falcon to the lineup wouldn't be just adding blacks for affirmative action's sake, any more than it could be considered catering to feminists to add Wasp or Ms. Marvel or Scarlet Witch. These are PART of the Avengers, and always were.

Avengers have always been on that "diversity train." The current MCU lineup is just the locomotive driving that train --- there's a ton of cars pulling behind it.